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boulder/cmd/notify-mailer
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Daniel McCarney 8efc6342bb Mailer reliability improvements (#2262) 
### Connect before sending mail, not at startup

Per #2250 when we connect to the remote SMTP server at start-up time by calling `mailer.Connect()` but do not actually call `mailer.SendMail()` until after we have done some potentially expensive/time-consuming work we are liable to have our connection closed due to timeout.

This PR moves the `Connect()` call in `expiration-mailer` and `notify-mailer` to be closer to where the actual messages are sent via `SendMail()` and resolves #2250 

### Handle SMTP 421 errors gracefully

Issue #2249 describes a case where we see this SMTP error code from the remote server when our connection has been idle for too long. This would manifest when connecting to the remote server at startup, running a very long database query, and then sending mail. This commit allows the mailer to treat SMTP 421 errors as an event that should produce a reconnect attempt and resolves #2249.

A unit test is added to the mailer tests to test that reconnection works when the server sends a SMTP 421 error. Prior to b64e51f and support for SMTP 421 reconnection this test failed in a manner matching issue #2249:

```
go test -p 1 -race --test.run TestReconnectSMTP421
github.com/letsencrypt/boulder/mail
Wrote goodbye msg: 421 1.2.3 green.eggs.and.spam Error: timeout exceeded
Cutting off client early
--- FAIL: TestReconnectSMTP421 (0.00s)
  mailer_test.go:257: Expected SendMail() to not fail. Got err: 421
  1.2.3 green.eggs.and.spam Error: timeout exceeded
  FAIL
  FAIL  github.com/letsencrypt/boulder/mail     0.023s
```

With b64e51f the test passes and the client gracefully reconnects.

The existing reconnect testing logic in the `mail-test-srv` integration tests is changed such that half of the forced disconnects are a normal clean connection close and half are a SMTP 421. This allows the existing integration test for server disconnects to be reused to test the 421 reconnect logic.
 		2016-10-20 14:10:47 -04:00
..
testdata Support Reg ID intermediate form for notify mails (#1958) 2016-07-12 16:01:38 -07:00
main.go Mailer reliability improvements (#2262) 2016-10-20 14:10:47 -04:00
main_test.go `notify-mailer` graceful handling of `sql.ErrNoRows`. (#2185) 2016-09-19 12:14:48 -07:00